Breast cancer is a malignant neoplasm that develops from the epithelial cells of ducts and lobules of the glandular parenchyma, which according to the World Health Organization (WHO) is the most common form of cancer among women (16% of all cases) in the world. In 2014, in Kaluga, Lipetsk, Smolensk and Tula regions the mortality from breast cancer reached 3.2%, 3.1%, 4% and 4.7%, respectively. One of the aggressive forms of breast cancer is a HER2positive (HER2+) subtype (14 to 20% of all subtypes), which is treated with targeted therapy. The appearance of trastuzumab for subcutaneous administration has a number of advantages compared to the intravenous formulation. A pharmacoeconomic analysis of treatment of HER2+ breast cancer was performed by comparing trastuzumab in two formulations in Kaluga, Lipetsk, Smolensk and Tula regions. According to the "cost minimization" analysis in the analyzed regions, the use of trastuzumab for subcutaneous administration compared to intravenous administration saves from 29.7 to 34% of funds. The forecasted budget savings as a result of the budget impact analysis for 10 patients is 8,068,360 rubles in Kaluga region, 7,047,430 rubles in Lipetsk region, 6,534,750 rubles in Smolensk region, and 7,188,980 rubles in Tula region for the treatment course with trastuzumab in subcutaneous formulation as compared to the intravenous formulation. The results showed that the use of trastuzumab therapy in the subcutaneous formulation allows treatment of 4 additional patients with HER2+ breast cancer in Smolensk region, and 5 patients in Kaluga, Lipetsk and Tula regions within a fixed budget.